Investigating the relationship between cell size and rate of diffusion

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Investigating the relationship between cell size and rate of diffusion

Aim: To plan and carry out an investigation to show the relationship between volume, surface area, and diffusion; and to demonstrate, using diffusion, why the size of cells is limited.

Hypothesis: In this experiment, I expect to find that when the surface area to volume of a cell reaches a certain level, diffusion alone won’t be able to supply the cell materials needed, and as single-celled organisms take in and release substances by means of diffusion across the cell membrane, this process limits cell size. I predict that as the rate of diffusion will be too slow to deliver materials to the center of the cell in the larger cells, it could result in cell malfunction.

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Variables: In this investigation, the variable I am manipulating, the independent variable are the dimensions of surface area to volume ratio of the agar cube. The variable I am observing/recording, the dependent variable, is the rate of diffusion (NaOH turns the agar cube pink as it disperses into it). The controlled variables will be keeping the concentrations of the Sodium Hydroxide constant, to use agar jelly from the same batch (so the type of agar jelly is exactly the same), and to keep the time even for all cubes so the NaOH has the same amount of time to disperse ...

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** The investigation does not really address the central question of the effect of surface area to volume ratio in enough detail. Too much focus is placed on the calculation of the surface area to volume ratio and its relationship with the size of the cube. The data from the experiment is missing. The discussion does approach the reason why a high surface area to volume ratio is important as it allows faster diffusion rates which is vital for cell functioning. It does not really explain that the more surface area that is available compared to volume means that there is more of its volume exposed to the outside environment and that this increases diffusion rate.